1. Field of the Invention
The present invention relates to a display apparatus and a control method for the display apparatus, and particularly to a display apparatus using a light emitting element which is driven by an electrical current, as well as to a control method for the display apparatus.
2. Description of the Related Art
An image display apparatus using an organic light emitting diode (abbreviated as OLED) is called an organic EL display and has been known as an image display apparatus using a light emitting element which is driven by an electrical current and has its luminescence intensity controlled in accordance with an amount of the electrical current. This organic EL display has drawn attention for its thinness, light weight, capability of high-speed response and therefore its application as a high-performance thin display apparatus which provides favorable viewing angles and high image quality with less electricity.
However, the OLED in this organic EL display, which is driven by an electrical current, has decreasing luminance due to a trap level that is generated as the electrical current is applied to the OLED. In order to restore such decreased luminance of the OLED, a method of, for example, applying a reverse bias voltage to the OLED is conventionally used. As the method of applying a reverse bias voltage, there has been proposed a method of setting conditions for application of such reverse bias voltage as to restore the decreased luminance of the OLED, and applying the reverse bias voltage under the set conditions (see Patent Reference 1: Japanese Unexamined Patent Application Publication 2005-301084, for example). According to this method of applying the reverse bias voltage, a certain application condition is set, and under the set application condition, the reverse bias voltage is applied, which allows for restoration of the decreased luminance of the OLED. The conventional method, however, has a problem that decreased luminance of the OLED cannot be restored properly. With this method, it is not possible to extend the life of the OLED.
To be specific, in the conventional method, the application of the reverse bias voltage at a constant level according to a certain application condition may, in some cases, result in application of an extraordinary high reverse bias voltage. Such application of an extraordinary high reverse bias voltage causes a sudden change of potential from high forward potential to high reverse potential, thereby leading to instantaneous flow of a large inrush current through the OLED. This instantaneous flow may cause deterioration or breakdown of the OLED. Moreover, setting the application condition for every application of the reverse bias voltage involves enormous amounts of calculation, resulting in a huge load on a control system.
For this reason, in the conventional method, the reverse bias voltage cannot be applied properly, which causes a problem that decreased luminance of the OLED may not be restored optimally. In such a case, it is not possible to extend the life of the OLED.